The present invention relates to swage type fasteners including a pin or mandrel and a collar adapted to be swaged into a locking portion of the pin and more specifically to a unique form of swage type fastener for use in applications such as a weld stud joint and a related fastening system and method.
Many structures are fastened together with swage type fasteners of a lockbolt type, including a pin and a collar, such as shown in U.S. Pat. No. 2,531,048 issued to L. C. Huck on Nov. 21, 1950 for "Fastening Device", U.S. Pat. Re. No. 30,445 issued to John H. Ruhl on Dec. 16, 1980 for "Fastener With Proportioned Strength Lock Grooves", and U.S. Pat. No. 4,472,096 issued to John Ruhl and Richard D. Dixon on Sep. 18, 1984 for "Optimized Fastener Construction System and Method".
The latter type fasteners are set by an installation tool which applies a relative axial force between the pin and collar via engagement of the collar by a swage anvil and gripping of a pull portion on the pin with a jaw assembly; as the axial force increases the swage anvil on the tool moves axially and radially overengages the collar swaging it into lock grooves in the pin. As the axial force increases further the pull portion or pintail of the pin is severed at a reduced strength portion or breakneck groove and the swaged collar is then ejected from the anvil to complete the installation. Typically the lock grooves are annular, i.e. in a non-threaded form, and thus the swaged connection would not be as susceptible to loosening from vibration as in the case of a threaded connection, i.e. nut and bolt. Even so, however, it is believed that a collar swaged into lock grooves which are in the shape of a thread form are less susceptible to loosening from vibration than the threaded connection from a standard nut and bolt. The present invention while utilizing the swage collar concepts is directed to a unique structure and unique applications such as for use in a weld stud joint. Conventionally a weld stud can be a bolt like member having a head and a threaded shank; the head is adapted to be welded to a support plate or surface to define a threaded stud adapted to cooperate with a nut member to threadably secure other members or workpieces. An example of a weldable stud can be seen in U.S. Pat. No. 4,850,772 issued to J. C. Jenkins on Jul. 25, 1989 for "Friction-Weldable Stud".
In some applications the fastened joint is subject to severe vibrations which could loosen the threaded connection. At the same time it is desirable that the workpieces which are secured by the threaded nut and stud combination be able to be removed for repair, replacement and/or access without damaging the stud and that the joint be secured again with the same stud. This requires that the nut be removable from the stud without damaging the threads on the stud shank. Also in some applications it is desirable that the clamp load applied to the workpieces between the nut and threaded stud shank be relatively low.
As noted, typically in a lock bolt, the collar is swaged into annular lock grooves and hence would not be susceptible to loosening from vibration as with a threaded nut and bolt. Thus a swaged connection would be advantageous if the swaged collar could be removed without damaging the shank and if a new collar could be swaged onto the stud shank when the joint is put together again. In fact tools are available to remove a collar which has been swaged onto a lockbolt like pin without damaging the pin. The above objectives, then, are accomplished by the unique swage collar with pintail structure (pintailed collar) of the present invention. In addition the fastener can be constructed such that the workpieces are clamped together at a relatively low clamp load. In one form of the invention a unique swage anvil is provided with a preselected stop shoulder to limit the axial travel, and hence length of radial overengagement, of the swage anvil relative to the collar member. This combination provides control of the extent of collar member swaged and hence control of the final clamp force exerted on the workpieces. This also assists in providing consistent severance of the excess portion of the pintail structure and collar member.
It is desirable that the amount of protrusion of the weld stud fastener assembly beyond the workpieces secured together be predictable and, in some cases, be minimized. With a threaded weld stud member and associated nut the final protrusion of the set fastener is generally determined by the length of the weld stud member regardless of the overall thickness of workpieces being secured. This can also be accomplished with the pintailed collar of the present invention.
In the present invention a unique weld stud member can be provided for use with the pintailed collar. In one form of the invention, the weld stud member is provided with one or more gripping grooves at its free end which will initially mechanically bond the collar member to the stud member at a relatively low swage load and hence low relative axial force. With this initial mechanical bond the collar member is held onto the stud member and will not be pulled off and into the swage anvil as the relative axial force increases during swage of the collar member onto the larger diameter portions of the pin. This feature is especially important where the degree of reduction of collar material in swage is quite great in order to provide good fill of the associated lockgroove. The present invention then provides a unique weld stud or pin member for use with the pintailed collar. In addition the present invention provides a unique fastening system and method for implementing such system.
While the unique swageable collar member with a pintail is shown as specifically applied in a unique combination with a unique weld stud member it should be understood that such collar member with pintail can be used in combination with other pin or mandrel type members in similar or different applications.
Thus it is an object of the present invention to provide a unique swage type fastener including a swageable collar member with a pintail.
It is another object of the present invention to provide a unique swage type fastener including a unique weld stud member and a swageable collar member with a pintail.
It is another object of the present invention to provide a unique fastening system including a unique swage type fastener including a swageable collar member with a pintail and an installation tool with a unique swage anvil.
It is a general object of the present invention to provide a unique swage type fastener and fastened joint.
It is still another object of the present invention to provide a unique method for implementing the noted fastening systems.